Excellent game I once owned back in 1997.

Classic turn-based sci-fi strategy game. 

For more info see: http://www.mobygames.com/game/fallen-haven

Extract from the afore mentioned website:
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Turn-based strategy and tactics defines the gameplay for sci-fi game Fallen Haven. The game centers around humanity's defense of colony planet New Haven on the fringes of the galactic battleground. Taurans, the opposing alien race, arrive in force with dropships and advanced weaponry to try and unseat the well-entrenched human foe.

Gameplay begins with a strategic planning phase where research and development and logistical planning takes place. The tactical gamplay phase places more emphasis on fire and movement of a wide variety of human and alien infantry, vehicles, artillery, and flyers. Players can also build defensive fortifications, roadways, and bases to bolster their chances at victory.

The game features multiple difficulty levels, an expansive battle-map with 15 territories and can be played from either side (Human or Tauran). While the game is turn based its core mechanics play very similarly to a traditional real-time strategy game. Music included with Fallen Haven is CD quality techno that is well suited to the game style.
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I have played this game so I can confirm it works! However, I have run it in Windows 98 and Windows XP, not Vista so I cannot vouch for Vista compatibility but seeing as this game was made for Windows 95 and it runs on XP i suppose it might very well also work on Vista.

Good luck.
Happy downloading and playing.

M.